Kar Kantar was one of several "petty warlords" said to be among those in power in the Qiris sector at the turn of the 25th century. They had gotten hold of an "antique" Romulan Bird-of-Prey, and were running wild from Vashti to Daimanta.
In 2399, they launched an attack against former admiral Jean-Luc Picard, aboard La Sirena using this Romulan Bird-of-Prey. La Sirena was assisted by an unidentified ship, which enabled them to turn the tide and cripple Kantar's ship. (PIC: "Absolute Candor")
This character was not seen on-screen.